1. Field of the Invention
This invention relates to an auxiliary tank for collecting excess volatile liquids, such as gasoline, during the filling of an underground storage tank and particularly to a containment tank which prevents seepage of such liquids into the ground, and a cover which prevents surface water from entering the containment tank.
2. Description of the Relevant Art
Presently known auxiliary holding tanks for catching spillage of gasoline when filling main storage tanks include small cylindrical upper containers mounted around the fill pipes for the main underground storage tanks with an opening at ground level closed by a manhole cover. The cover may have no seal around the rim, may have a resilient O-ring seal to prevent water leakage into the tank, or may have a skirt which admits water but traps air in the container to prevent water from entering the fill pipe. Additional seals are provided between the fill pipe and the bottom of the container to prevent gasoline from entering the ground below the tank while permitting movement due to varying weather conditions. Drain pipes are also employed to empty the excess gasoline into the fill pipe and main tank. Examples of such devices are found in U.S. Pat. No. 4,520,852, 4,491,147, 4,278,115 and 4,457,349, with a commercially available device known as the OPW 84 Series Spill Container being manufactured by the Dover Corporation of Cincinnati, Ohio. Another more recent commercial device is a containment box manufactured by CNI Manufacturing of Irwindale, Calif., which includes a cover that does not permit entry of water into the containment area. None of these devices, however, include a simplified structure which permits surface water to be bypassed around the cover into a space between an inner container and outer skirt and cover support into the ground with means extending across the space to secure the inner container to the outer skirt and cover support, and also permits use of larger size tanks having extended upper plates with a relatively small area cover spaced from the outer rim.